1. Field of the Invention
The present invention relates to a connected construction of a high-frequency package and a wiring board and, more particularly, to a connected construction of a high-frequency package and a wiring board wherein the high-frequency package and the wiring board can be electrically connected without degrading the transmission characteristic of high-frequency signals of 20 GHz and higher.
2. Description of the Relevant Art
A conventional high-frequency package is constructed by a semiconductor device mounting area and a high-frequency circuit on the periphery of the device, both of which are formed on a dielectric substrate, being sealed with a ring-shaped frame and a lid to be arranged thereon. A semiconductor device mounted on the semiconductor device mounting area is connected to signal lines formed so as to pass through the sidewall portion of the frame. Connecting the signal lines of the high-frequency package with the semiconductor device mounted thereon to signal lines of a wiring board makes it possible to input and output high-frequency signals from and to the outside of the package. In that connection between the high-frequency package and the wiring board, the formation of a package construction and signal lines, which make it possible to input and output high-frequency signals without degrading the high-frequency signal characteristics, is required.
FIGS. 18(a) and 18(b) are schematic diagrams showing a conventional connected construction of a high-frequency package and a wiring board of this type, and FIG. 18(a) is a sectional side view, while FIG. 18(b) is a sectional perspective view along line Bxe2x80x94B of FIG. 18(a).
A dielectric substrate 41 is formed almost in the shape of a rectangular parallelepiped board having a thickness of T. A ground 42 is formed on the bottom surface 41b of the dielectric substrate 41, while a ring-shaped frame 44 made of dielectrics is formed in a prescribed place on the top surface 41a of the dielectric substrate 41. A plurality of thin-film-like circuit strips 43a having a width of w1 are formed in prescribed places on the dielectric substrate top surface 41a in the frame inside region 44d, while lead strips 43b similar to those (having a width of w1) are formed in the outside region 44e, facing the circuit strips 43a with the frame 44 between. One end portions of the circuit strips 43a and one end portions of the lead strips 43b are connected through connecting strips 43c having a width of w2, which are buried within a wall portion 44a of the frame 44. A signal line 43 comprises these circuit strip 43a, lead strip 43b, and connecting strip 43c. 
In order to equalize the characteristic impedance of a circuit comprising the connecting strip 43c and the wall portion 44a thereabout to those of the circuit strip 43a and the lead strip 43b, the width w2 of the connecting strip 43c is set to be smaller than the widths w1 of the circuit strip 43a and the lead strip 43b. In order to hold down the return loss in the signal line 43 and to make the transmission loss smaller, each characteristic impedance in the circuit strip 43a, lead strip 43b and connecting strip 43c is matched to one another.
A semiconductor device 45 is mounted almost in the center of the dielectric substrate top surface 41a in the frame inside region 44d, and pads 45a of the semiconductor device 45 and the other end portions of the circuit strips 43a are connected through bonding wires 45b. A lid 46 is joined onto the top of the frame 44 (hermetic sealing), and the frame inside region 44d on the dielectric substrate 41 is sealed thereby. A high-frequency package 40 of a microstrip line type comprises these dielectric substrate 41, ground 42, signal lines 43, frame 44, lid 46, and associated parts.
The lead strip 43b of the signal line 43 of the high-frequency package 40 is electrically connected to one end of a signal line 52 formed on a wiring board 50 through an outer lead terminal 53.
In that connected construction, high-frequency signals (not shown) are input from the signal line 52 of the wiring board 50 through the outer lead terminal 53, the lead strip 43b, connecting strip 43c and circuit strip 43a of the signal line 43 of the high-frequency package 40, and associated parts, and reach the semiconductor device 45, while high-frequency signals emitted from the semiconductor device 45 of the high-frequency package 40 are output from the circuit strip 43a of the signal line 43 through the connecting strip 43c and lead strip 43b thereof, and the outer lead terminal 53 to the signal line 52 of the wiring board 50.
However, in the connected construction of the high-frequency package 40 and the wiring board 50 as stated above, it is extremely difficult to equalize the characteristic impedance in the outer lead terminal 53 to those in the signal lines 43 and 52. Therefore, the characteristic impedance mismatch becomes large between the outer lead terminal 53 and the signal line 52 on the wiring board 50 as well as between the outer lead terminal 53 and the lead strip 43b of the signal line 43 of the high-frequency package 40. As a result, the signal reflection caused by the characteristic impedance mismatch at the junction between the outer lead terminal 53 and the signal line 52 on the wiring board 50, and that at the junction between the outer lead terminal 53 and the signal line 43 of the high-frequency package 40, becomes large. In order to cope with the problem, a connected construction has been proposed, wherein signal lines of a high-frequency package and signal lines of a wiring board are directly connected without using outer lead terminals for connecting the high-frequency package to the wiring board, through improvements in the interconnection structure of the signal lines of the high-frequency package and the like.
In Japanese Kokai No. 2000-164764, it has been disclosed that a high-frequency package and a wiring board can be connected without degrading the transmission characteristic of high-frequency signals by forming connecting pads on both sides of each connected portion of signal lines of the high-frequency package and those of the wiring board, both having transmission lines of a transmission mode of microstrip, and arranging connecting conductive vias (through hole conductors) to connect a ground layer formed within the high-frequency package to a ground layer formed within the wiring board through the connecting pads.
FIG. 19 is a sectional side view showing the connected construction of a high-frequency package and a wiring board described in the Japanese Kokai No. 2000-164764. FIGS. 20(a)-(c) are schematic diagrams showing the principal part of the connected construction of a high-frequency package and a wiring board shown in FIG. 19, wherein FIG. 20(a) is a top plan view of the high-frequency package, FIG. 20(b) is a bottom plan view thereof, and FIG. 20(c) is a top plan view of the wiring board.
Reference numeral 61 in the figure represents a dielectric substrate made of ceramics or the like. A cap-shaped lid 62 is joined to a prescribed place on the top surface of the dielectric substrate 61 through a seal portion 63. A plurality of signal lines 64 are formed in prescribed places on the top surface of the dielectric substrate 61 in the inside region 62a of the lid 62, and each one end of the signal lines 64 is connected to a semiconductor device 65.
Within the dielectric substrate 61, a ground layer 66 is formed across the dielectric substrate 61 except for slots 66a, and a microstrip line as a third high-frequency transmission line C is formed from the ground layer 66 and the signal line 64.
In addition, signal lines 67 are formed in prescribed places on the bottom surface of the dielectric substrate 61, and a microstrip line as a first high-frequency transmission line A is formed from the signal line 67 and the ground layer 66. Connecting pads 68 are formed on both sides with one end portion 67a of the signal line 67 between, and a connection 69 is formed from the one end portion 67a of the signal line 67 and the connecting pads 68. The connecting pads 68 and the ground layer 66 are connected by through hole conductors 70. The electromagnetic coupling of the first signal transmission line A and the third signal transmission line C is established through the slot 66a, and signals are transferred between both of the lines A and C. A high-frequency package 60 comprises these dielectric substrate 61, signal lines 64, ground layer 66, signal lines 67, lid 62, and associated parts.
Reference numeral 80 in the figure represents a wiring board for mounting the high-frequency package 60 thereon. On the top surface of a dielectric substrate 81 constituting the wiring board 80, signal lines 82 as second high-frequency transmission lines B and connecting pads 83 on both sides thereof are formed in the positions which are matched to those of the connections 69 formed on the underside of the dielectric substrate 61 of the high-frequency package 60. Within the dielectric substrate 81, a ground layer 84 is formed, and the connecting pads 83 and the ground layer 84 are connected by through hole conductors 85. Concave portions 81a are formed on the surface of the wiring board 80.
By making the first high-frequency transmission lines A on the bottom surface of the high-frequency package 60 faced with the second high-frequency transmission lines B on the top surface of the wiring board 80, bonding the one end portions 67a of the signal lines 67 to one end portions 82a of the signal lines 82 using a bonding material 71 such as a solder, and bonding the connecting pads 68 to the connecting pads 83 as well, a connection between the high-frequency package 60 and the wiring board 80 is provided.
It has been disclosed that, in the connected construction of the high-frequency package 60 having those connecting pads 68 and through hole conductors 70 and the wiring board 80 having those connecting pads 83 and through hole conductors 85 as stated above, the connectivity between the high-frequency package 60 having transmission lines of a transmission mode of microstrip, wherein a signal is transferred by electromagnetic coupling, and the wiring board 80 having transmission lines of a transmission mode of microstrip similarly can be improved, so that it is possible to suppress the degradation of the insertion loss S21 in a frequency band of 30 GHz-40 GHz, compared with the case wherein the high-frequency package 60 is connected to a wiring board with no through hole conductor 85 formed therein.
In the connected construction of the high-frequency package 40 and the wiring board 50 shown in FIG. 18, as described above, the return loss of a signal in the connection through the outer lead terminal 53 increases, so that the signal cannot be transferred efficiently. Particularly in bands of sub-millimeter wavelengths and shorter, exceeding 20 GHz frequency, it is impossible to maintain a favorable transmission characteristic.
In the connected construction of the high-frequency package 60 and the wiring board 80 shown in FIGS. 19 and 20, a reduction in insertion loss S21 in a frequency band of 30 GHz-40 GHz has been confirmed, so that the transmission characteristic (insertion loss S21) has been improved. However, at 40 GHz and higher frequencies, the transmission characteristic is liable to be greatly degraded, and in a band of 40 GHz and higher frequencies on the higher frequency side, the transmission characteristic cannot be improved.
The present invention was developed in order to solve the above problem, and it is an object of the present invention to provide a connected construction of a high-frequency package and a wiring board having an excellent high-frequency transmission characteristic, without degrading the transmission characteristic of even high-frequency signals in a wide band ranging from 20 GHz to 80 GHz frequency in the case of connecting a high-frequency package to a wiring board.
As described above, in a conventional connected construction of a high-frequency package and a wiring board, high-frequency signals in a wide band ranging up to a high-frequency band of about 80 GHz could not be transmitted without degrading the transmission characteristic.
The present inventors paid their attention to the distances between conductive vias formed on a high-frequency transmission line substrate constituting a high-frequency package and between those formed on a wiring board, and found that by setting the distance between the conductive vias formed on the high-frequency package and the distance between the conductive vias formed on the wiring board in consideration of the dielectric constant of each dielectric substrate constituting each substrate, it is possible to transmit high-frequency signals on the higher frequency side without degrading the transmission characteristic thereof, leading to the completion of the present invention.
In order to achieve the above object, a connected construction of a high-frequency package and a wiring board (1) according to the present invention is characterized by both a first distance, between first conductive-via rows to connect first grounds formed on both main surfaces of a high-frequency transmission line substrate constituting a high-frequency packages, and a second distances, between second conductive-via rows to connect second grounds formed on both main surfaces of a wiring board on which the high-frequency package is mounted, being set in consideration of the dielectric constant of the high-frequency transmission line substrate and that of the wiring board in order to improve the high-frequency transmission characteristic between the high-frequency transmission line substrate and the wiring board.
Using the above connected construction of a high-frequency package and a wiring board (1), the increase in return loss in the connection between the high-frequency package and the wiring board can be held down and the transmission loss can be reduced, so that a connected construction of a high-frequency package and a wiring board having an excellent transmission characteristic over a high-frequency region of shorter wavelengths can be achieved.
A connected construction of a high-frequency package and a wiring board (2) according to the present invention is characterized by Wp and Wb being set in the range of Wp less than xcex0/(2xc3x97∈r11/2) and Wb less than xcex0/(2xc3x97∈r21/2), where ∈r1 is the dielectric constant of the high-frequency transmission line substrate, ∈r2 is the dielectric constant of the wiring board, xcex0 is the wavelength in a vacuum of a high-frequency signal propagating through signal lines, Wp is the distance between the first conductive-via rows, and Wb is the distance between the second conductive-via rows in the above connected construction of a high-frequency package and a wiring board (1).
Using the above connected construction of a high-frequency package and a wiring board (2), it is possible to prevent the occurrence of resonance which is caused by the distance Wp between the first conductive-via rows in a high-frequency signal emitted in a direction almost perpendicular to the signal lines formed on the high-frequency transmission line substrate, and to prevent the generation of ripples. And it is also possible to prevent the occurrence of resonance which is caused by the distance Wb between the second conductive-via rows in a high-frequency signal emitted in a direction almost perpendicular to the signal lines formed on the wiring board, and to prevent the generation of ripples.
Accordingly, the increase in return loss in the connection between the high-frequency package and the wiring board can be held down and the transmission loss can be reduced, so that a connected construction of a high-frequency package and a wiring board having an excellent high-frequency transmission characteristic over a high-frequency region of shorter wavelengths can be achieved.
In addition, the present inventors found that by adjusting the widths of gaps and signal lines in a joined portion of a high-frequency package and a wiring board, as the distance between first conductive-via rows formed on the high-frequency package and the distance between second conductive-via rows formed on the wiring board are set in consideration of the dielectric constant of each dielectric substrate constituting each substrate, the mountability can be improved and that the transmission characteristic can be made more excellent as well.
A connected construction of a high-frequency package and a wiring board (3) according to the present invention is characterized by the high-frequency package having first signal lines and first gaps interposed between the first signal lines and the first ground on one main surface side of the high-frequency transmission line substrate, and second signal lines, one end thereof being joined to the wiring board and the other end thereof being connected to the first signal line through a third conductive via, and second gaps interposed between the second signal lines and the first ground on the other main surface side of the high-frequency transmission line substrate. The wiring board has a third signal line and a third gap interposed between the third signal line and the second ground on the joined surface side to the high-frequency package. The width of the second gap in a joined portion of the high-frequency package and the wiring board is set to be larger than that of the second gap except in the joined portion, and/or the width of the third gap in the joined portion is set to be larger than that of the third gap except in the joined portion in the above connected construction of a high-frequency package and a wiring board (2).
Using the above connected construction of a high-frequency package and a wiring board (3), the width of the second gap in the joined portion is set to be larger than that of the second gap except in the joined portion, and/or the width of the third gap in the joined portion is set to be larger than that of the third gap except in the joined portion, so that it is possible to hold down the decrease in impedance of the second signal line and/or the third signal line in the joined portion, and to improve the impedance matching in the joined portion. Particularly, the increase in return loss in an intermediate-frequency band (10 GHz-40 GHz) can be further held down, leading to a further improvement in the transmission characteristic.
Here, it is more favorable to make the width of the second gap in the joined portion as large as possible so that the impedance of the second signal line in the joined portion can be made closer to that of the second signal line except in the joined portion (usually 50xcexa9), but the upper limit thereof is necessarily limited by the distance between the first conductive-via rows. Similarly, it is more favorable to make the width of the third gap in the joined portion as large as possible so that the impedance of the third signal line in the joined portion can be made closer to that of the third signal line except in the joined portion (usually 50xcexa9), but the upper limit thereof is necessarily limited by the distance between the second conductive-via rows.
Because of the widened gap widths, the activity of connecting the high-frequency package to the wiring board can be done easily, and the occurrence of poor connections such as a short circuit can be more certainly prevented, leading to an improvement in mountability.
A connected construction of a high-frequency package and a wiring board (4) according to the present invention is characterized by the relationships 0 less than Dpxe2x89xa6xcex0/4(∈r1/2+1/2)1/2 and/or 0 less than Dbxe2x89xa6xcex0/4(∈r2/2+1/2)1/2 which hold, where Dp is the length of a portion of the second gap, the width thereof being set to be larger in the longitudinal direction of the second signal line, being added to the joined portion on the high-frequency transmission line substrate, and Db is the length of a portion of the third gap, the width thereof being set to be larger in the longitudinal direction of the third signal line, being added to the joined portion on the wiring board in the above connected construction of a high-frequency package and a wiring board (3).
Using the above connected construction of a high-frequency package and a wiring board (4), the lengths Dp and Db are set so that the above relationships hold. Therefore, it is possible to hold down the decrease in impedance of the second signal line and/or the third signal line in the gap portions extended by the lengths Dp and Db, the widths thereof being set to be larger. As a result, the impedance matching between the second and third signal lines in the joined portion can be further improved.
In addition, since a margin of the length Dp or Db can be added to the width of the joined portion, the activity of connecting the high-frequency package to the wiring board can be done more easily, and the occurrence of poor connections such as a short circuit can be further reduced, leading to a further improvement in mountability.
A connected construction of a high-frequency package and a wiring board (5) according to the present invention is characterized by a prescribed region ranging from the end portion on the third-conductive-via connecting side of the first signal line to one side plane on the wiring-board connected side on the high-frequency transmission line substrate, wherein the first ground is not formed in the above connected construction of a high-frequency package and a wiring board (3) or (4).
Using the above connected construction of a high-frequency package and a wiring board (5), the first ground is not formed in the prescribed region, so that the capacitive component between the second signal line and the first ground, and that between the third signal line and the first ground can be made smaller. As a result, particularly, the degradation of the transmission characteristic in a high-frequency region can be prevented and the impedance matching can be achieved across a much higher frequency region, leading to the realization of a connected construction of a high-frequency package and a wiring board having an excellent transmission characteristic.
A connected construction of a high-frequency package and a wiring board (6) according to the present invention is characterized by the prescribed region including at least a portion facing the second signal line between the end portion on the third-conductive-via connecting side of the first signal line and the one side plane on the wiring-board connected side in the above connected construction of a high-frequency package and a wiring board (5).
Using the above connected construction of a high-frequency package and a wiring board (6), the capacitive component between the second signal line and the first ground, and that between the third signal line and the first ground can be further smaller. As a result, by holding down the decrease in impedance related to the second signal line on a higher frequency side, the impedance matching in the joined portion can be improved.
A connected construction of a high-frequency package and a wiring board (7) according to the present invention is characterized by a lid for sealing the high-frequency package, or a frame formed on a sealing portion, being made of an insulating material when the prescribed region overlaps the sealing portion of the high-frequency package in the above connected construction of a high-frequency package and a wiring board (5) or (6).
Using the above connected construction of a high-frequency package and a wiring board (7), the effect of preventing the degradation of the transmission characteristic in a high-frequency region, which can be obtained through not forming the first ground in the prescribed region, can be obtained with reliability.